If `A ,\ B ,\ C` are the angles of a triangle, prove that : `cos A+cos B+cos C=1+r/Rdot`

If A,B,C are the angles of a triangle then prove that cosA+cosB-cosC=-1+4cos(A/2)cos(B/2)sin(C/2)

If A, B and C are interior angles of a triangle ABC, then show that sin((B+C)/2)=cos(A/2)

If A , B and C are interior angles of triangle ABC ,then show that sin ((B+C)/( 2) )=cos (A) /(2)

If A, B and C are angles of a triangle such that angleA is obtuse, then show tan B tan C lt 1.

If DeltaABC is a right angle triangle then prove that cos^(2)A+cos^(2)B+cos^(2)C=1iffsin^(2)A+sin^(2)B+sin^(2)C=2

For any triangle ABC, prove that : a(cosC-cosB)=2(b-c)cos^(2)""(A)/(2)

If 3tan A tan B=1, prove that 2cos(A+B)=cos(A-B)dot

For any triangle ABC, prove that : (b+c)cos((B+C)/(2))=acos((B-C)/(2))

If on a given base B C , a triangle is described such that the sum of the tangents of the base angles is m , then prove that the locus of the opposite vertex A is a parabola.

The sides of a triangle are in AP. If the angles A and C are the greatest and smallest angle respectively, then 4 (1- cos A) (1-cos C) is equal to